A defiant Rep. Todd Akin today rejected calls from Republican presidential candidate Mitt Romney and running mate Paul Ryan to drop out of the Missouri Senate race over his controversial comments about rape and pregnancy.

Akin let a 6 p.m. ET (5 p.m. CT) deadline pass without withdrawing his name from the ballot.

"As of 5 p.m. there's been no withdrawal filed," the secretary of state's office told ABC News. "[Akin] would have to have a court order now to get off the ballot."

Akin can still drop out of the race. Under Missouri law, he has until Sept. 25 to obtain a court order for his withdrawal, but it would require Akin to pay for a reprinting of ballots.

"Let me make it absolutely clear," Akin said on Mike Huckabee's radio show. "We're going to continue with this race for the U.S. Senate."

Akin wasn't swayed by appeals from Romney and Ryan as well as five current and former Missouri senators.

"Today, his fellow Missourians urged him to step aside," Romney said in a statement. "I think he should accept their counsel and exit the Senate race."

On Monday, Ryan had a five minute phone call with Akin urging him to consider stepping down.

"He didn't ask him to get out," the source said. "He said, basically, 'You need to reflect on this and think about what is best for you, your family and things you believe in.'"

When that didn't work Ryan today endorsed Romney's suggestion that Akin quit the race.

Instead, Akin posted an online video seeking "forgiveness" for saying that women rarely get pregnant from what he called "legitimate rape."

"By taking this stand, this is going to strengthen our country," he told Huckabee, calling in to the show for the second straight day. "It will strengthen the Republican Party."

"We can't run from our shadows," he said later during an interview with Missouri-based conservative talker Dana Loesch.

High-ranking GOP officials fear Akin's inflammatory words have sunk his chances of winning the Missouri race and may also scuttle Republicans' hopes of taking control of the Senate.

Earlier today, Akin gained an unlikely ally in the form of Democratic rival Sen. Claire McCaskill.

McCaskill, who is trailing Akin in the polls, said that Republican leaders should not be trying to overturn the results of the Republican primary that made Akin their candidate.

"Elections are sacred," McCaskill told St. Louis Fox affiliate KTVS. "There was an election, so I think the voters of Missouri should be respected, not have some big-wig, fancy people from Washington come in here and threaten him that he's got to drop out."

"It should not be lost on anyone that some of the only voices not calling for Congressman Akin to do the right thing and step aside are Claire McCaskill and the leaders of the pro-abortion movement," they said in a statement. "Senator McCaskill knows that the only way she wins re-election is if Todd Akin is her opponent in November."

Among the big-name Republicans asking Akin to quit are his would-be colleagues, including Missouri's junior senator Roy Blunt, who issued a joint statement together with former Missouri U.S. senators John Ashcroft, Kit Bond, John Danforth, and Jim Talent.

"The issues at stake are too big, and this election is simply too important. The right decision is to step aside," they wrote.

Senate Minority Leader Mitch McConnell, Maine's Republican Sen. Olympia Snowe, Kelly Ayotte of New Hampshire and Richard Burr of North Carolina have all joined the chorus.

McConnell called Akin's initial remarks a "deeply offensive error at a time when his candidacy carries great consequence for the future of our country... To continue serving his country in the honorable way he has served throughout his career, it is time for Congressman Akin to step aside."

Todd Akin Won't Quit Missouri Senate Race After Rape Remark

On Monday, Sens. Scott Brown of Massachusetts, Ron Johnson of Wisconsin and Texas's John Cornyn, head of the National Republican Senate Committee, urged Akin to step aside. Additional pressure came from Karl Rove's powerful Crossroads GPS Super PAC which said it will pull all of its money out of Missouri if Akin stays in and the Tea Party Express which released a statement calling for Akin to "step down."

Akin tried to salvage his candidacy today by releasing a video asking voters for "forgiveness."

"Rape is an evil act" and "the mistake I made was in the words I said, not in the heart I hold," Akin tells voters in the video.

"Governor Romney and Congressman Ryan disagree with Mr. Akin's statement, and a Romney-Ryan administration would not oppose abortion in instances of rape," the campaign said yesterday, before dialing up the rhetoric.

Earlier today, the Republican National Convention approved a plank in their platform advocating for the passage of the "Human Life Amendment," which would ban abortion in all circumstances, even in cases of rape or incest.

It employs the same language that was used in the party platform in 2004 and 2008.